A typical cooling system expansion tank is a closed vessel which, when the engine is at rest, is only partially filled with liquid coolant, the remainder of the space above the liquid being available for the volumetric expansion of the coolant due to heat. Coolant discharged from the engine flows into the tank and returns from the tank to join the flow of coolant returned to the engine. Such an expansion tank also serves as a means of enabling gasses dissolved or trapped in the coolant to rise to the liquid surface and escape. The expansion tank also usually incorporates a filler cap with a two-way valve which sets the maximum pressure in the cooling system and allows the intake of air if a negative pressure develops. Such a filler cap is usually known as a pressure cap.
However, the inventors herein have recognized several issues with such an approach. As one example, in the design of such expansion tanks the pressure at the outlet as dictated by the pressure cap, and may, in extreme engine running conditions, be insufficient to prevent cavitation at the circulating pump. An object of the invention is to provide a cooling system expansion tank which overcomes or alleviates this problem.
Thus, in one example, the above issues may be addressed by providing an expansion tank for the cooling system of a liquid-cooled internal combustion engine, the tank comprising a housing which includes a cylindrical wall defining a swirl chamber, an inlet connection on the housing for connection to a supply of coolant discharged from the engine, the inlet connection being arranged to duct coolant to an inlet orifice opening into the swirl chamber, an outlet connection on the housing for the return of coolant to the engine, the outlet connection being arranged to duct coolant from a collector duct having an entrance opening into the swirl chamber, the inlet orifice and the collector duct being arranged such that when the tank is in use, coolant may be discharged into the swirl chamber in a direction tangential to the cylindrical wall, and coolant may be directed along the cylindrical wall into the collector duct. In some examples, the cylindrical wall may be arranged with its axis substantially vertical.
Conveniently, the housing defines a main chamber and the swirl chamber is positioned within the main chamber. In such an arrangement the swirl chamber may have an outlet aperture opening into the main chamber and positioned above the inlet orifice and the collector duct. The swirl chamber may also have an inlet aperture opening from the main chamber and positioned below the inlet orifice and the collector duct, preferably substantially on the axis of the swirl chamber.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.